1. Field
The disclosure relates to an electric power receiving device and an electric power transmission device.
2. Description of Related Art
Various types of electric power transmission systems for contactlessly or wirelessly transmitting electric power from an electric power transmission device to an electric power receiving device have been proposed.
The power receiving device includes an electric power receiving unit including a resonance circuit, and a case that houses the power receiving unit, and the resonance circuit includes a power receiving coil and a power receiving capacitor. The power transmission device includes an electric power transmission unit including a resonance circuit, and a case that houses the power transmission unit, and the resonance circuit includes a power transmission coil and a power transmission capacitor.
Generally, the resonance circuit of each of the power receiving unit and the power transmission unit consists of one coil, and one capacitor connected to the coil.
If AC current is passed through the series LC resonance circuit, the voltage of the capacitor and the voltage of the coil vary according to the frequency of the AC current. At this time, the voltage phase of the capacitor and the voltage phase of the coil are in the reversed state. For example, the voltage rises in the coil when the voltage drops in the capacitor, and the voltage drops in the coil when the voltage rises in the capacitor. As a result, during transmission of electric power, the absolute value of a voltage at a connection point of the coil and the capacitor is larger than the absolute values of voltages at the other portions of the resonance circuit.
Since the absolute value of the voltage at the connection point of the coil and the capacitor is large, as described above, the absolute value of the average voltage of the resonance circuit as a whole becomes large.
Therefore, if a member, such as a case, is located around the resonance circuit of each of the power receiving unit and the power transmission unit, a potential difference between the resonance circuit and the case is large. In particular, a potential difference between the connection point of the capacitor and the coil and the case is large.